Abstract

Self-harm and suicidal behaviour are common reasons for emergency
department presentation. Those who present with self-harm have an elevated
risk of further suicidal behaviour and death.

Aims

To examine whether a postcard intervention reduces self-harm
re-presentations in individuals presenting to the emergency department.

Method

Randomised controlled trial conducted in Christchurch, New Zealand. The
intervention consisted of six postcards mailed during the 12 months following
an index emergency department attendance for self-harm. Outcome measures were
the proportion of participants re-presenting with self-harm and the number of
re-presentations for self-harm in the 12 months following the initial
presentation.

Results

After adjustment for prior self-harm, there were no significant differences
between the control and intervention groups in the proportion of participants
re-presenting with self-harm or in the total number of re-presentations for
self-harm.

Conclusions

The postcard intervention did not reduce further self-harm. Together with
previous results this finding suggests that the postcard intervention may be
effective only for selected subgroups.

Emergency department presentations for self-harm and attempted suicide are
increasing in a number of countries, including the USA, UK and New
Zealand.1–4
Those who present to hospital with self-harm are at increased risk of a range
of negative outcomes, including further self-harm and
death.5–7
A systematic review found repetition rates for self-harm after an index
hospital visit for non-fatal self-harm were 16% within the first year and 23%
within 4 years; the rate of suicide in the 9 years following self-harm was
almost 7%.7 These
high rates of morbidity and mortality in those presenting with self-harm have
prompted the development of interventions to reduce the risk of further
suicidal behaviour following a hospital self-harm presentation. Interventions
shown to significantly reduce further suicidal behaviour include follow-up
telephone
calls,8,9
cognitive therapy10
and psychodynamic interpersonal
therapy.11 However,
some of these interventions are time consuming and costly to deliver. An
easily administered, low-cost alternative is the ‘postcard’
intervention, first proposed by
Motto,12,13
and more recently evaluated by
Carter.14,15
Carter’s trial consisted of eight postcards mailed to participants
during the 12 months following their hospital admission for self-poisoning. In
a randomised controlled trial (RCT), the postcard intervention almost halved
the number of readmissions for self-poisoning in the intervention group in the
12 months following the index admission, with this reduction maintained for 24
months after the index admission. However, the benefits of the postcard
intervention appeared to be confined to a relatively small subsample of
participants. Specifically, the reduction in readmission rates in the
intervention group appeared to be almost entirely the result of a large
reduction in the number of repeat visits among women who were frequent
self-poisoning repeaters. These results suggested that the effectiveness of
the postcard intervention may be confined to selected subgroups of individuals
who self-harm (female frequent emergency department attenders, people who live
alone and/or are socially isolated); further trials are necessary to establish
the effectiveness of the intervention in different patient groups.

The aim of our study was to examine whether a postcard intervention reduced
self-harm re-presentations to the psychiatric emergency service in a sample of
individuals presenting to this service in Christchurch, New Zealand, following
an episode of self-harm.

Method

Study population

The recruitment population consisted of all individuals aged 16 and older
who presented to psychiatric emergency services at Christchurch Hospital, New
Zealand, following self-harm or attempted suicide during the period 1 August
2006 to 6 April 2007. The psychiatric emergency service is an acute
psychiatric service affiliated with Christchurch Hospital and its staff see
all individuals presenting to the Christchurch Hospital emergency department
with self-harm or suicide attempts. Christchurch Hospital emergency department
is the sole emergency department in the greater Christchurch area, serving a
population of approximately 500 000 people.

Eligible patients were those who presented to the psychiatric emergency
service following self-harm or attempted suicide, were normally resident at a
New Zealand address, and were able to speak English sufficiently well to
understand the study. Written informed consent was obtained from all
participants prior to commencement of the study. The study was approved by the
Upper South B Regional Ethics Committee. Eligibility for the study was
assessed by the psychiatric emergency service’s clinicians based on a
psychiatric interview conducted as part of standard practice, which included
mental status examination, psychiatric history and questions about current and
previous suicide attempts and self-harm. Prior to enrolling individuals in the
study, dedicated research staff who were not psychiatric emergency service
clinicians checked eligibility by reviewing the department’s
records.

Intervention

Participants were randomised 1:1 by research staff into two groups
(treatment as usual; treatment as usual plus the postcard intervention) using
predetermined computer-generated random numbers. The psychiatric emergency
service clinicians were masked to treatment allocation. Treatment as usual
consisted of crisis assessment and referral to in-patient community-based
mental health services. The intervention consisted of a series of six ‘
postcards’ sent by mail during the 12 months following the
participant’s index presentation for suicide attempt or self-harm. The
text and format of the postcard were based on those used by Carter and
colleagues.14,15
The postcard read: ‘It has been a short time since you were
here at PES (Psych Emergency), and we hope things are going well for you. If
you wish to drop us a note we would be happy to hear from you’. (We used
six rather than the eight postcards Carter used for several reasons: no strong
justification has been presented for eight postcards; we were seeking to
establish the minimum number of postcards that would be effective so that the
intervention could be translated to a real-world situation in which
secretarial staff would send the postcards routinely, and, based on
consultation with Carter, who suggested earlier postcards might be the
effective element, we decreased the number of later, and thereby, overall,
postcards).

Postcards were printed on A4 paper and posted in a plain sealed envelope to
the participant’s residential address. Postcards were posted at the
following times after the index presentation: 2 and 6 weeks; 3, 6, 9 and 12
months. The envelope included a return address so that undelivered postcards
could be returned. The return address consisted only of a code and a post
office box number so that the source of the letter could not be identified
from the outside of the envelope. When a postcard was returned research staff
endeavoured to obtain the participant’s new address using both the
contact details that the participant had provided at the index interview, and
contact details from the departmental records. If a new address was found for
the participant, the letter was re-sent to the new address. If no new address
could be found for the participant, the letter was not re-sent.

Sample size and power

Initial power calculations, based on estimated re-presentation rates of 20%
for the control group and 12% for the intervention group, yielded a required
sample size of 700 (350 per group) in order to detect differences at the
P<0.05 level with 80% power. Recruitment was therefore commenced
with a planned sample size of 700. However, after 8 months of recruitment,
inspection of preliminary results revealed a larger than anticipated
difference between intervention and control groups in the rate of
re-presentation to the psychiatric emergency service for further self-harm. In
addition, over the first 8 months of the trial there had been ongoing
difficulties with recruitment procedures, with clinical staff reluctant to
recruit participants to the trial. Therefore, consideration was given to
stopping the trial early. The P required for overall type I error of
0.05 with one interim test was calculated to be 0.015 using the Fleming,
Harrington and O’Brien
boundary.16
Comparison of the rate of further self-harm in the intervention and control
groups revealed that the difference was significant at P<0.001
(mean number of further psychiatric emergency service visits per 100 people:
14.4 v. 33.3, odds ratio (OR) = 0.43). Therefore, the trial was
stopped after 8 months of recruitment with a sample size of 327.

Measures

Demographic data

Baseline demographic information including age, gender, marital status and
method of self-harm was collected as part of the standard procedures of the
psychiatric emergency service.

History of self-harm

Participants’ hospital medical records were reviewed to identify any
presentations to Christchurch Hospital emergency department for self-harm in
the 12 months prior to the index presentation.

Outcome measures

Re-presentations for self-harm were assessed by monitoring two sources of
re-presentation information. First, psychiatric emergency service records were
checked daily by research staff to identify attendances by study participants.
Second, participants’ hospital medical records were reviewed at the
conclusion of the 12-month follow-up period to identify visits to Christchurch
Hospital emergency department for self-harm in the year following the index
presentation. Three measures of re-presentation were calculated from these
data: re-presentations to psychiatric emergency service, re-presentations to
Christchurch Hospital emergency department and total re-presentations to
either the psychiatric emergency service or emergency department.

Assignment and masking

Randomisation was based on a random number sequence available only to
research staff. The number sequence was computer-generated in SAS 9.1 for
Windows using a uniform distribution to generate a sequence of random numbers
between 0 and 1. Numbers of 0.5 or above were classified as the intervention
group; numbers below 0.5 were classified as the control group. Randomisation
was performed post-recruitment and post-consent by research staff who were not
involved in the recruitment or clinical care of participants.
Participants’ randomisation status was not conveyed to clinical or
data-collection staff. Clinical staff assisted participants to complete the
forms required to enrol in the study. Completed forms were forwarded to
research staff daily. Research staff then allocated participants to the
control or intervention group based on the pre-generated random number
sequence. In order to prevent duplicate enrolments, clinical staff checked
details of eligible individuals against a list of participants who had already
enrolled in the study. This list was updated daily. Participant details were
checked against the list again by research staff prior to randomising
participants.

Statistical analysis

All statistical analysis was performed in SAS 9.1 for Windows. The results
of the trial were analysed using the intention-to-treat design. Comparisons of
rates of re-presentation in the control and intervention groups were conducted
by fitting a Poisson regression in which the number of re-presentations was
modelled as a function of randomisation status. Comparisons of the proportions
of individuals re-presenting in the control and intervention groups were
conducted by fitting a logistic regression in which the log odds of
re-presentation was modelled as a function of randomisation status.
Adjustments for prior self-harm were made by including the number of prior
self-harm presentations as a covariate in the regression model.
Covariate-adjusted re-presentation rates were calculated using the methods
described by
Lee.17

Results

Participant flow and follow-up

A total of 541 people were eligible for the study during the recruitment
period. Of these, 327 were enrolled (a recruitment rate of 60.4%); 153
participants were randomised to the intervention group and 174 randomised to
the control group. For the majority of participants, self-harm involved
self-poisoning (n = 250 (76.7%); cutting: n = 47 (14.4%);
hanging: n = 11 (3.4%); vehicle exhaust carbon monoxide poisoning:
n = 6 (1.8%); motor vehicle crash: n = 6 (0.9%); other
methods: n = 9 (2.7%)). Figure
1 summarises the flow of participants through the study.

Analysis

Table 1 compares self-harm
re-presentations for the intervention and control groups over the 12-month
follow-up period. The intervention and control groups are compared on two
re-presentation measures: the proportion of participants re-presenting at
least once for self-harm during the follow-up period; and the total number of
self-harm re-presentations per 100 people over the follow-up period. For each
measure, re-presentation was assessed in three ways: re-presentations to the
psychiatric emergency service; re-presentations to the emergency department;
and total re-presentations to either the psychiatric emergency service or
emergency department.

Re-presentation for self-harm in the 12 months following the index
presentation

The postcard intervention was not associated with a significant reduction
in the proportion of participants re-presenting to the emergency department
(OR = 0.92, P>0.75) or in the total proportion of participants
re-presenting to either the psychiatric emergency service or the emergency
department (OR = 0.87, P>0.58). The intervention was, however,
associated with a significant reduction in the proportion of participants
re-presenting to the psychiatric emergency service (OR = 0.57,
P<0.06). When re-presentation was measured using the total number
of re-presentations over the 12-month follow-up period, the intervention was
associated with a significant reduction in the number of re-presentations to
psychiatric emergency service (incident risk ratio, IRR = 0.46,
P<0.0001). The intervention was also associated with reductions in
the total number of re-presentations to the emergency department (IRR = 0.75,
P<0.04) and to either the psychiatric emergency service or the
emergency department (IRR = 0.73, P<0.03), although the
significance of these effects was marginal due to P exceeding the
adjusted boundary P value of 0.015.

Although the results in Table
1 indicated that the intervention was associated with a reduction
in the total number of self-harm re-presentations in the 12-month follow-up
period, it is important to consider whether this difference arises from
pre-existing differences between the two groups.
Table 2 compares the control
and intervention groups on a series of demographic and background factors,
reporting P for significance from a t-test for independent
means (for the continuous measures) or a chi-squared test for independence
(for the dichotomous measures).

Comparison of control and intervention groups at the time of the index
presentation

There were no significant differences between the intervention and control
groups in age, gender, marital status, method of self-harm, length of hospital
stay or history of attendance for self-harm in the 12 months prior to the
index presentation (all P>0.12). However, there was a significant
difference between the groups in the number of prior attendances for self-harm
in the previous 12 months (P<0.07), with the number of prior
attendances being lower in the intervention than in the control group.

The results in Table 2
suggest that the reduced number of re-presentations for self-harm in the
intervention group reported in Table
1 may reflect a pre-existing tendency for those in the
intervention group to have lower numbers of prior hospital attendances for
self-harm. Therefore, we adjusted re-presentation rates in
Table 1 for the total number of
hospital attendances for self-harm in the 12 months prior to study entry.

Table 3 shows the proportion
of participants re-presenting, and the adjusted total number of
re-presentations, in the 12-month follow-up period in the control and
intervention groups, adjusted for number of hospital visits for self-harm in
the 12 months prior to study enrolment. Adjusting for the number of prior
hospital visits for self-harm reduced, and in many cases removed, the effect
of the intervention on re-presentation for self-harm. After adjustment, there
was no significant difference between control and intervention groups in the
proportion of participants re-presenting with self-harm to the psychiatric
emergency service (OR = 0.64, P>0.13), to the emergency department
(OR = 1.04, P>0.88) or to either the psychiatric emergency service
or the emergency department (OR = 0.97, P>0.91). Furthermore, the
intervention was not associated with a reduction in the total number of
re-presentations for self-harm to the emergency department (IRR = 1.10,
P>0.52) or to either the psychiatric emergency service or the
emergency department (IRR = 1.07, P>0.64). The intervention was
associated with a reduction in the total number of re-presentations to the
psychiatric emergency service (IRR = 0.65, P<0.04), but the
significance of this effect must be considered marginal because the P
for significance exceeds the adjusted boundary P value of 0.015.

Re-presentation for self-harm in the 12 months following the index
presentation, adjusted for prior self-harm

Discussion

The results of this RCT suggested that a postcard intervention did not
significantly reduce self-harm re-presentations in individuals presenting to a
psychiatric emergency service following an index episode of self-harm.
Although unadjusted results suggested that the postcard intervention reduced
the total number of self-harm re-presentations in the 12 months following the
index presentation, comparison of control and intervention groups revealed
that the intervention group had lower rates of self-harm presentations in the
12 months prior to trial entry. Adjusting for this pre-existing difference in
prior self-harm removed the apparent effect of the intervention. These results
suggest that any reduction in rates of further self-harm presentations in the
intervention group in this trial could be explained by pre-existing
differences between the control and intervention groups in their history of
self-harm. When these pre-existing differences were accounted for, the
postcard intervention did not reduce the rate of self-harm re-presentations in
the 12 months following the index presentation. A marginally significant
reduction in the number of re-presentations to the psychiatric emergency
service was not substantiated by measures of re-presentation taken from
hospital records.

Comparison with previous studies

The results of this study contrast with those from a previous RCT conducted
by Carter and
colleagues14,15
who reported that a postcard intervention reduced the total number of
self-poisoning re-presentations by almost half in the 12 months following the
index presentation, with this effect persisting for 24 months. The findings
from our trial suggested that a very similar intervention did not reduce
further self-harm re-presentations in the 12 months following the index
presentation. Several possibilities may account for this discrepancy. The
first is that the postcard intervention is more effective following
self-poisoning than following other types of self-harm. The sample of
participants in Carter’s study was restricted to those presenting with
self-poisoning, whereas the sample used in our study included those presenting
with any method of self-harm. However, although individuals presenting with
any method of self-harm were eligible for our study, the final sample
consisted primarily (77%) of self-poisoning presentations. Analyses (not
presented here) of only those who self-poisoned in our study found no
significant reduction in re-presentations among those receiving the
intervention.

Another possibility is that differences in treatment procedures and
healthcare structures between the two study sites may have resulted in the
intervention being differentially effective in the two different settings.
Although Carter’s study did not reveal the mechanism of action of the
intervention, the authors suggested that postcards may be effective by
enhancing a sense of social connectedness. The ability of the postcard
intervention to increase feelings of social connectedness may be influenced by
the overall treatment model, the level of support already available, and other
similar factors that could be expected to vary across treatment settings.
Therefore, it is possible that the effectiveness of the postcard intervention
depends on the characteristics of the treatment setting, and the intervention
may not effectively reduce further self-harm presentations in all
settings.

Implications

This study highlights the importance of cross-checking key outcome measures
in RCTs using multiple data sources. The results of this study suggested that
the postcard intervention was associated with a reduction in the number of
re-presentations to psychiatric emergency service for self-harm. However,
cross-checking psychiatric emergency service data against hospital medical
records suggested that re-presentations recorded in the psychiatric emergency
service data were only a subset of the total re-presentations to the
psychiatric emergency service and the emergency department. When these
additional visits were considered, results suggested that the postcard
intervention did not reduce the total number of re-presentations for
self-harm.

This study also highlights the importance of testing for the possibility of
pre-existing differences between control and intervention groups, even when
apparently adequate randomisation and masking procedures have been used. Our
study demonstrates that, in some cases, the apparent effects of an
intervention may be explained by pre-existing differences in background
characteristics between control and intervention groups.

Initial trial results and early stopping

A feature of this trial is that it was stopped early in response to interim
data that suggested that the postcard intervention was associated with a large
and statistically significant reduction in the number of self-harm
re-presentations to the psychiatric emergency service. However, the final
trial results contrasted with these interim findings and provided no evidence
that the intervention significantly reduced the total number of self-harm
re-presentations. This discrepancy between the interim and final results
appears to be as a result of two factors. First, the interim data only
assessed re-presentations to the psychiatric emergency service and did not
include information about re-presentations to the emergency department.
Cross-checking the psychiatric emergency service data with the emergency
department data at the time of the final analysis revealed that
re-presentations recorded in the psychiatric emergency service data were only
a subset of the total number of re-presentations. Second, the interim data
were not adjusted for history of self-harm because information about prior
presentations for self-harm was not available at the time that recruitment was
stopped. Had these additional sources of data been available at the time of
the interim analysis, the outcome of the decision about early stopping may
have been different. This suggests, therefore, that decisions regarding the
early stopping of RCTs should be based on the widest range of data available,
including baseline data that may indicate pre-existing group differences, and
outcome data from multiple sources to enable cross-checking.

Staff reluctance to initiate change

Another reason for stopping this trial early was the reluctance of clinical
staff to recruit individuals to the trial. We suspect this was part of a more
generic institutional reluctance to change, and highlights the types of
problems to be faced in conducting research projects in real-world
settings.

Limitations

A limitation of this study was that, despite apparently strong
randomisation and masking procedures, there remained a pre-existing difference
between intervention and control groups in the history of prior hospital
visits for self-harm. There is no apparent reason for this difference, given
that individuals were randomised post-consent and all clinical and data
collection staff were masked to participants’ allocations. As in
previous studies of hospital presentations for self-harm for example, see
Carter et
al15 and Hall
et al,18
the distribution of prior self-harm presentations in this study was skewed,
with most participants having no prior presentations, and a small number of
participants having a very high number of prior presentations. This
distribution means that the inclusion of a very small additional number of
individuals with high-frequency self-harm in one experimental group can have a
substantial effect on overall rates of prior self-harm in that group. For this
reason, it may be useful for future trials to adopt a stratified randomisation
procedure, such as that used by Vaiva et
al,9 in which
participants are split into two strata (low number of prior self-harm
presentations and high number of prior self-harm presentations) prior to
randomisation, and the randomisation process is then completed separately for
each stratum.

It could be suggested that given the decision to terminate the study early,
the present findings are as a result of the study being underpowered, and that
had recruitment continued according to the original design, clear benefits of
the intervention might have been observed. However, the findings from the
reduced sample suggest that any possible benefits of the intervention were at
best very modest and in most cases non-existent. It seems unlikely this
conclusion would alter even with a substantially larger sample.

These limitations notwithstanding, the results of the current study suggest
that the postcard intervention did not reduce self-harm re-presentations among
those presenting to a general hospital psychiatric emergency service following
self-harm. The results of further trials of postcard interventions may help to
clarify whether this type of intervention effectively reduces self-harm
re-presentations, and the specific patient groups and treatment settings in
which the intervention is most effective.

Funding

This study was supported by grants from the Canterbury
District Health Board and the Accident
Compensation Corporation (ACC). S.J.G. was supported by a
University of Otago Postgraduate Publishing
Bursary.

Acknowledgments

We gratefully acknowledge the assistance of the staff from Psychiatric
Emergency Services of the Canterbury District Health Board.